I am a new member here. What a great forum you have here?
I am going to flash my 8600GT VGA cards which are running as SLI in ASUS M2N32-SLI Deluxe. Is there any problems related to two graphic cards? Or it will be done in order?
Or else?

If it were me I would take one card out (and blow out the heatsink, since it's outside of the case anyway), flash the card I left in, then take that card out and put the unflashed one in, clean out the flashed card... flash the unflashed card then throw both cards in. Great, two flashed cards with clean heatsinks.